Answer:
There was no chart, but I will help you, this answer might not the correctly answer, because this is what I had learned in the history class.
Explanation:
The causes is flea and people were dirty in Medieval Europe, when the city was all dirty, there must have many fleas and mouse, the fleas drink the blood from mouses and pass the virus to the mouses. When the mouses get the virus, they will be dangerous, they eat the food and run in the house, that make the houses have the virus too, so the virus will speed in the city, then another city, city to city, country to country. If people get virus, their body will have some black small ball appear, people will die if they didn't get the treatment.
